Wireless access systems and radio access technologies (RATs) have been developed to provide different types of services. Some examples of the wireless access systems include wireless local area networks (WLANs), (such as IEEE 802-based networks), and cellular networks, (such as universal mobile telecommunication systems (UMTS) terrestrial radio access network (UTRAN), an evolved UTRAN (E-UTRAN), a GPRS/EDGE radio access network (GERAN), or the like).
With the pervasive adoption of wireless communication networks in enterprise, residential and public domains, users of such networks may move from one network to another while enjoying continuous connectivity. Wireless transmit/receive units (WTRUs) (e.g., mobile stations, user equipments, etc.) are required to support multiple heterogeneous networks to support an “always-on” scenario. Thus, a seamless handover between these networks is therefore important.